1. Field of the Invention
The present invention relates to an optical disk apparatus for recording or reproducing the information on an optical disk, or in particular to a technique for controlling the actuator of an optical pickup.
2. Description of the Related Art
The conventional techniques related to this invention are described in JP-A-2003-51128, JP-A-2003-157554 and JP-A-2003-99925. JP-A-2003-51128 describes a technique for attenuating the amplitude level of a light detector detection signal before gain adjustment in the mean servo system to stabilize the actual control operation in accordance with the servo signal and the sum signal for high-speed recording in an optical disk. JP-A-2003-157554 describes the technique in which a tracking error signal is generated by removing the frequency component of not less than one half of the sampling frequency of an analog-to-digital converter in the average servo system in order to eliminate the amplitude adjustment error to assure stable tracking servo control in the average servo system even in the case where the tracking error signal becomes a high-frequency signal and attenuated on the one hand and the amplification factor of a gain amplifier is variably controlled in order that the amplitude of the output signal of a gain amplifier substantially coincides with a reference amplitude value on the other hand. Also, JP-A-2003-99925 describes the technique in which in order to accurately detect the wobble signal at low cost and accurately regardless of the recording conditions for recording the information in an optical recording medium, a wobble signal detection unit includes a sample-and-hold means for sampling and holding a photoelectric conversion signal and accurately removing the noise component not related to the wobble signal, and a high-frequency band limiting means for removing the high-frequency component of not less than the cut-off frequency in the photoelectric conversion signal, wherein any of the techniques is activated in accordance with the recording conditions.